Organic electroluminescence (EL) elements have a structure in which an organic layer containing a light-emitting layer is sandwiched between two sheets of electrodes. Organic EL elements emit light when current flows the organic layer. The organic layer may comprise a carrier injection layer, a carrier transport layer and a carrier blocking layer in addition to the light-emitting layer, on both sides thereof.
One of the known techniques of forming the organic layer of organic EL elements is an ink-jet (IJ) method. With the IJ method, a red light-emitting segment, a green light-emitting segment and a blue light-emitting segment of a light-emitting layer which constitutes a pixel of the organic EL elements can be form as fine patterns without requiring the so-called patterning. The ink used for the IJ method generally contains, as solute, an organic EL material which is relatively easily dissolve to an organic solvent.
However, the solute dissolved in such ink precipitates with time by external factors such as light, air and temperature, which may likely cause problems including clogging of ink in the ink-jet head.